Light Dependent Regulation of Sleep/Wake States by Prokineticin 2 in Larval Zebrafish

Citation

Chen, Shijia (2016) Light Dependent Regulation of Sleep/Wake States by Prokineticin 2 in Larval Zebrafish. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z99P2ZNR. https://resolver.caltech.edu/CaltechTHESIS:08082015-121950812

Abstract

Sleep is an evolutionarily conserved behavior and essential to survival. The classic two process model of sleep regulation proposes that sleep results from the interaction between circadian and homeostatic processes, but the details remain elusive. Most sleep research is performed using nocturnal rodents, and diurnal vertebrates are under-represented. It is unclear whether circadian regulatory mechanisms of sleep in nocturnal animals can be directly translated into diurnal animals. In this thesis, I first briefly describe sleep behavior and the two process model of sleep regulation, focusing on the circadian process, and then discuss the advantages of using larval zebrafish as a model to study sleep behavior in diurnal vertebrates. In Chapter 2, I characterize the role of Prokineticin 2, a proposed circadian output factor in nocturnal animals, in sleep/wake regulation in larval zebrafish. I show that, similar to nocturnal rodents, Prok2 is both necessary for daytime sleep/wake behavior and sufficient to modulate sleep/wake states in a light dependent manner. However, unlike nocturnal rodents and similar to humans, Prok2 is not required for maintaining circadian rhythmicity in larval zebrafish after removing external light cue. This result demonstrates the potential functional difference of circadian output factors in different chronotypes, and establishes larval zebrafish as an alternative model for studying circadian regulation of sleep and possibly other behaviors in humans. In Chapter 3, I describe the adaptation and development of TRP channels to manipulate neuronal activity in larval zebrafish, in an effort to expand the existing repertoire of genetic tools for studying behavior in zebrafish. I show that three TRP channels, TRPV1, TRPM8 and TRPA1, can inducibly activate specific populations of neurons in larval zebrafish by using their appropriate agonists. At high agonist concentrations, TRPV1, can rapidly induce cell ablation. Adaptation of TRP channels for use in larval zebrafish expands the variety of behavioral experiments and combinatorial manipulation of neuronal activity that can be performed in zebrafish. In summary, this work deepens our understanding of sleep regulation, establishes larval zebrafish as an appropriate model for studying circadian regulation of sleep in diurnal vertebrates, and presents novel genetic tools for studying behavior in larval zebrafish.

Thesis Files